118 IOWA ACADEMY OF SCIENCES. 



southeastern corner of the county, near the limit of the Wis- 

 consin drift, and there are occasional exposures in Franklin 

 and Washington townships, along the tributaries of the Skunk 

 river and Squaw creek, in the west central portion of the region. 

 It is to the latter occurrence that it is desired to direct atten- 

 tion. 



The best exposures may be viewed on sections 5 and 34, in 

 Washington township, along Clear and Walnut creeks respec- 

 tively. 



The Walnut creek section shows: feet. 



Drift, yellowish above, bluish below (Wisconsin) 20 



Loess, sandy below 20 



Clay, blue with much coarse gravel exposed 



The loess is silicious throughout and the upper four feet is 

 distinctly joined and stained a faint yellow-brown along the 

 joint planes. It grades downward into a massive, structureless, 

 pale blue clayey silt which contains, in places, an abundance 

 of root casts, wood fragments and black. Carbonaceous spots 

 and emits a distinct swamp like odor. The entire deposit is 

 highly calcareous and carries a rich gastropod fauna. Prof. 

 B. Shimek identified the following forms, the majority of 

 which are strictly terrestrial. 



Zonitokles shbnekli, (Pilsbry) P. & J. 



Spliyradmm edentulnm alt kola, (Ingersoll) P. &. J. 



Pupa muscoruiii, L. 



Bifidarki jjentodo)), (Say) Sterbi. 



Vertigo ovata, Say. 



Co'i 'ulus fu Ivus , (Mull). 



Polygyra multilineata, (Say) P. & J. 



Pyramidula striateUa, (Anth.) P. &. J. 



Vallonia costata, (Mull) Sterbi. 



Succinea lineata, Binn. 



Succinea avara, Say. 



Limna'a hroiulis, Say? 



Loess concretions are relatively scarce and are diminutive in 

 size. The deposit shows no signs of oxidation or leaching 

 where the drift covering is thick; but where the covering 

 is so far reduced as to afford imperfect protection from the 

 w^eathering agents, both leaching and oxidation may be noted, 

 and here, alone, are lime concretions to be found. It is obvious 

 that little or no alteration took place prior to the deposition of 

 the overlying drift. 



